Historically, connecting rods have been machined on transfer lines using fixtures to hold the parts while machining. The fixtures have used a 3-2-1 locating and clamping method. This employs three point locating on the thrust face or side of the connecting rod with opposed clamps, two locating points on the pin end and one side locator on the crank end.
A prior connecting rod transfer line has numerous fixtures required for all the drilling, reaming, boring and other operations. A problem with this fixture arrangement is that it is inflexible. When a change in engine design is made, it is common to change the crank bore diameter or the length of the connecting rod. In the past, this would involve a very costly change to a connecting rod line since new fixtures and other details would have to be changed to accommodate the new design. This could include, on the fixtures alone, new side locators and clamps and new crank bore locators and clamps for bore changes and new pin locators and clamps for length changes.
To reduce the cost and time delay of the conversion process, connecting rod lines are now in use with a two point crank bore equalizer to eliminate the need for a crank bore side locator which is dependent on the crank bore diameter. Also, some lines are being built that have a two or three position pin bore V-block on a turret. This will allow for machining two or three different known lengths of connecting rods on the same fixture.